Fluorine has been known as a substance which acts on the teeth to enhance the acid-resistance of the enamel, thereby reducing the incidence of dental caries. Conventionally, fluoride compounds such as sodium fluoride, stannous fluoride, and sodium monofluorophosphate are incorporated as fluorine sources in various oral compositions such as dentifrices, mouthrinses, and coating agents in such a way that they act on the surface of teeth, thereby allowing fluorine to exhibit its dental caries preventing effects.
Recent studies have reported that fluorine treatment applied in the early stage of dental caries accelerates remineralization, i.e., restoration of affected teeth to sound ones.
Fluorine-containing dentifrices, mouthrinses, and coating agents have the advantage of easy applicability but their retention in the mouth is not satisfactorily long and the period of time over which fluorine acts on the teeth is insufficiently short. Thus, the uptake of fluorine by the teeth is not high enough to warrant the intended efficacy. Since conventional dental caries-preventing fluorine coating agents employ water-soluble fluorides and are usually formulated in water-soluble dosage forms, they are unable to be retained in the mouth for a satisfactorily long period of time.
Methods have been attempted to improve the oral retention of fluorides by using thickening or gelling water-soluble high molecular weight compounds or by dispersing the fluoride in natural resins, but even such modified agents are unable to be retained in the mouth no more than several hours.
Methyl methacrylate based polymers and bis-GMA based polymers have been known for use as dental compositions such as fissure sealants and dental adhesives. These polymers are used after polymerization and curing having taken place in the mouth, such as by polymerization at ambient temperatures in the presence of benzoyl peroxide or tertiary amines, or by polymerization reaction initiated by ultraviolet or visible ray. In such in situ polymerization methods, some monomers will inevitably remain unreacted and cause deleterious effects to the patient. Furthermore, their applicability is poor because two pastes have to be mixed together or exposure to light is necessary to initiate the polymerization reaction. In addition to this poor applicability, the monomers are so unstable that they have a tendency to become sticky or solidify during prolonged storage, thereby failing to warrant the quality of the product.